textproduct: Rapid City

KEY MESSAGES

- Scattered to numerous severe storms possible this afternoon/evening, with the highest risk in northwestern SD. Main threats of very large hail, strong winds, and an isolated tornado or two possible.

- Isolated severe storms possible Sunday.

- Gradual warming trend through next week, with possible 100s by Friday.

DISCUSSION

(This Afternoon Through Friday) Issued at 1017 AM MDT Sat Jun 27 2026

Current upper air models show mild ridge over the midwest region and shortwave over the MT/WY area, upper low over the PAC NW. At the surface, low pressure sits over southeastern MT, with a frontal boundary stretching down through WY. Temperatures currently sit in the upper 60s and 70s, with breezy south to southeasterly winds this morning.

Shortwave and attendant sfc low / frontal boundary slides across the region today. No shortage of available energy today, with ML CAPE values 3000-4500 j/Kg for areas east and north of the Black Hills this afternoon, while southwestern to south-central SD sit in the 1500-3000 j/Kg range. Effective shear ranges from 30-45kts as well this afternoon, making for a good supercell development day. Storms today will be capable of large hail (2"+) and strong winds (70mph+). Tornado threat is also present today, with the RAP showing northwest into central SD 50-100 helicity, LCL's around 1000-1500 meters, and sig tor of 2-3 for northwestern SD. SPC has northwestern SD in a 10% tor, which is significant for our region. CAMs show storms popping in the 19-21Z timeframe mainly over MT and WY, moving northeast. Main severe threat will be over northwestern SD for our CWA, however CAMs do try to pop a couple cells over southwestern SD mid-afternoon. Severe threat is a bit lower over the Black Hills and Rapid City area, but cannot be counted out. Storm threat runs through midnight, but by late evening, should be located closer to central SD.

By Sunday, upper low is expected over the ID/MT region, with a more southwest flow over the forecast area, and another chance for storms more in the evening to Monday morning timeframe. Isolated severe storms may be possible again, however bit less energy and shear to support widespread severe storms.

With the upper low moving east of the Rockies, temperatures dip a bit for Sunday and Monday, though still in the upper 70s and 80s. Temperatures gradually climb during the week, as main ridge builds to the east of us, and shortwave ridge builds over the Rockies. By Friday, some areas could see temps climb to around 100. WPC heat risk climbs into the moderate-major range for Thursday and Friday.

AVIATION

(For the 00Z TAFS Through 00Z Sunday Evening) Issued At 536 PM MDT Sat Jun 27 2026

Ongoing strong to severe thunderstorms across western SD are producing wind gusts to 50+ knots or greater. These storms are moving to the northeast, so expect local MVFR cigs/vsbys with the stronger storms. The entire complex of storms is expected to move east of the area by 28/06z with VFR conditions there after. Look for westerly winds to increase after 28/15z.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.